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OPEN
Received: 26 August 2016 Accepted: 24 May 2017 Published: xx xx xxxx
The chloride/phosphate ratio combined with alkaline phosphatase as a valuable predictive marker for primary hyperparathyroidism in Chinese individuals Qianqian Wang, Xu Li, Haibing Chen, Haoyong Yu, Lianxi Li, Jun Yin, Jian Zhou, Ming Li, Qing Li, Junfeng Han, Li Wei, Fang Liu, Yuqian Bao & Weiping Jia The chloride/phosphate ratio (Cl/PO4) has been suggested to have a role in primary hyperparathyroidism (PHPT), but the associations between Cl/PO4 combined with ALP level and PHPT has not been well-studied. Our aim was to investigate the predictive value of combination Cl/PO4 with ALP for PHPT. A cross-sectional retrospective analysis was conducted to examine 172 patients diagnosed with PHPT categorized into two groups: normocalcaemic primary hyperparathyroidism (NPHPT) group and hypercalcaemia PHPT group. We found that Cl/PO4 levels and ALP levels in the NPHPT and hypercalcaemia PHPT group were both significantly higher than normal controls. Cl/ PO4 and ALP levels were an independent risk factor for PHPT. Cl/PO4 combined with ALP increased the receiver-operating characteristic curves (ROC-AUC) and the diagnostic value in NPHPT and hypercalcaemia PHPT group (0.913; 95% CI, 0.744–1.000 and 0.932; 95% CI, 0.897–0.966, respectively), specificity of 92.8% and sensitivity of 98%. In conclusion, combination Cl/PO4 with ALP might be a lowcost, simple, available predictive marker of PHPT in Chinese individuals, particularly Chinese remote region where the method used to measure PTH cannot be done. Moreover, due to serum calcium level in NPHPT, Cl/PO4 combined with ALP level measurement have great potential to predict significant occurrence of NPHPT. Primary hyperparathyroidism (PHPT) is characterised biochemically by an inappropriately elevated parathyroid hormone (PTH) level and it is one of the most common endocrine disorders affecting human health1. Using the serum calcium level, PHPT can be subdivided into normocalcaemic primary hyperparathyroidism (NPHPT) and hypercalcaemic primary hyperparathyroidism. Wills first used the term NPHPT in the 1960s1. NPHPT is characterised by normal serum calcium levels and consistently high PTH levels2. NPHPT is not a common type of PHPT. Persistently elevated PTH and hypercalcaemia are the diagnostic markers of PHPT3. Several studies have used the oral calcium load to diagnose PHPT inpatients with NPHPT and asymptomatic patients4, 5. However, in clinical, we found PTH testing did not appear in the conventional inspection indicators, and the PTH testing equipment are expensive and time-consuming. And some Chinese remote areas had no equipment measuring PTH, Simultaneously, although serum calcium was measured in most hospitals, but serum calcium level was normal in the NPHPT patients. To improve the diagnosis of PHPT, we need to find additional, simple markers for diagnosing PHPT.
Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, 200233, China. Qianqian Wang and Xu Li contributed equally to this work. Correspondence and requests for materials should be addressed to J.H. (email: [email protected]) or L.W. (email: [email protected]) Scientific Reports | 7: 4868 | DOI:10.1038/s41598-017-05183-6
1
www.nature.com/scientificreports/ Reeves introduced the concept of the chloride/phosphate ratio (Cl/PO4)6. Some studies found that Cl/PO4 was a good tool for distinguishing PHPT from other causes of hypercalcaemia7–10. Furthermore, Mismar et al.11 reported that Cl/PO4 was predictive in normocalcaemic patients in an Indian population. Katelina12 and McComb9 et al. suggested that alkaline phosphatase (ALP) is a membrane-bound enzyme associated with the mineralization of bone tissue. The serum ALP level is elevated in 96% of patients with primary hyperparathyroidism13. But there have been no study evaluating predicting diagnostic value of Cl/PO4 combined with ALP in PHPT. Therefore, this study investigated the value of the two indicators combinatiom measurement as an auxiliary diagnostic method for PHPT diagnosis in a Chinese population, especially for predicting significant occurrence of NPHPT.
Materials and Methods
Study Population. From January 2003 to March 2015, 172 patients with PHPT in the General Surgery
Department of Shanghai Jiao Tong University Affiliated Sixth People’s Hospital were enrolled in our study. According to Chinese guidelines, for PHPT definition we used as main criteria a PTH level >65 and the presence of parathyroid adenoma based on intraoperative frozen and postoperative pathology, but not calcium blood level. PHPT can be subdivided into NPHPT and hypercalcaemic primary hyperparathyroidism using the serum calcium level. The exclusion criteria were as follows: all PHPT patients treated without surgery; secondary hyperparathyroidism; vitamin D deficiency; renal disease; hypercalciuria caused by other diseases; the use of diuretics; liver disease and other causes of an elevated PTH. The subjects were divided into two groups according to the serum calcium levels: 151 had a high serum calcium and PTH, while 19 patients were defined as NPHPT. During the same period, 50 clinical check-up healthy subjects from medical examination center of Shanghai Jiao Tong University Affiliated Sixth People’s Hospital were enrolled in our study. The inclusive criteria for them is as follows: All these participants had normal PTH levels, not suffering from PHPT disease, no family history of PHPT, normal renal function, and none were receiving medications known to influence these parameters such as sodium, potassium, ALP, phosphorus, chloride, calcium and PTH. The exclusion criteria of the control group is as follows: Patients were excluded if they had any disease that could affect electrolyte disorder (e.g. cancer, liver disease, cacotrophy, renal insufficiency, hypovolaemia and dehydration). Participants with using any related drugs such as diuretics were also excluded from the study. The study was approved by the Human Research Ethics Committee of Shanghai Sixth People’s Hospital, all experiments were performed in accordance with relevant guidelines and regulations. Each participant gave written informed consent.
Anthropometric evaluation and biochemical measurements. General information on the 222 par-
ticipants, such as gender and age, was obtained through inquiry. Anthropometric parameters such as height, body weight, and blood pressure were measured and the Body Mass Index (BMI) was calculated as weight/height2. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured enzymatically on a Hitachi 7600 analyser (Hitachi, Tokyo, Japan). Serum sodium, potassium, alkaline phosphatase (ALP), phosphorus, chloride, and calcium were measured using automated techniques before surgery. ALP was detected by AMP buffer method of the ALP kit (KH-G-C-012) obtaining from Shanghai Kehua Bio-engineering Co., Ltd (Shanghai, China). The normal range for ALP is from 14 to 112 U/L. We calculated the chloride/phosphate ratio (Cl/PO4) as chloride (mEq/L)/phosphate (mg/100 mL). The total serum calcium levels used in our research was adjusted for albumin. The formula to use is: corrected calcium = measured total serum calcium in mg/dL + 0.8*(4.0- patient’s serum albumin concentration in g/dL). Serum PTH was measured by using an electrochemiluminescence immunoassay (ECLIA) on an Elecsys autoanalyser (E170; Roche Diagnostic, Mannheim, Germany). All biochemical values were measured from the same blood sample collected after an overnight fast. Related indicators were detected by Department of Medical Laboratory in Shanghai Jiao Tong University Affiliated Sixth People’s Hospital. And the detection methods of related indicators had not changed.
Statistical analyses. Statistical analysis was performed using SPSS for Windows software (ver. 17.0; SPSS Inc., Chicago, IL, USA). Normally distributed data are presented as means ± standard deviation (SD). Non-normally distributed data determined using the Kolmogorov–Smirnov test are expressed as medians and interquartile range (25–75%). Two groups were compared using Student’s unpaired t-test. The composition ratio of categorical variables was calculated using the chi-square test. Pearson’s correlation was used to evaluate the association among the Cl/PO4 ratio, ALP and other general biochemical parameters. To analyse whether Cl/ PO4 and ALP might be related to PHPT independently, we applied logistic regression models to adjust for other clinical and biochemical variables. The predictive performance of each model was assessed using area the under the receiver operating characteristic (ROC-AUC) curve with 95% confidence intervals (CI). All P-values were two-tailed and statistical significance was considered as P
OPEN
Received: 26 August 2016 Accepted: 24 May 2017 Published: xx xx xxxx
The chloride/phosphate ratio combined with alkaline phosphatase as a valuable predictive marker for primary hyperparathyroidism in Chinese individuals Qianqian Wang, Xu Li, Haibing Chen, Haoyong Yu, Lianxi Li, Jun Yin, Jian Zhou, Ming Li, Qing Li, Junfeng Han, Li Wei, Fang Liu, Yuqian Bao & Weiping Jia The chloride/phosphate ratio (Cl/PO4) has been suggested to have a role in primary hyperparathyroidism (PHPT), but the associations between Cl/PO4 combined with ALP level and PHPT has not been well-studied. Our aim was to investigate the predictive value of combination Cl/PO4 with ALP for PHPT. A cross-sectional retrospective analysis was conducted to examine 172 patients diagnosed with PHPT categorized into two groups: normocalcaemic primary hyperparathyroidism (NPHPT) group and hypercalcaemia PHPT group. We found that Cl/PO4 levels and ALP levels in the NPHPT and hypercalcaemia PHPT group were both significantly higher than normal controls. Cl/ PO4 and ALP levels were an independent risk factor for PHPT. Cl/PO4 combined with ALP increased the receiver-operating characteristic curves (ROC-AUC) and the diagnostic value in NPHPT and hypercalcaemia PHPT group (0.913; 95% CI, 0.744–1.000 and 0.932; 95% CI, 0.897–0.966, respectively), specificity of 92.8% and sensitivity of 98%. In conclusion, combination Cl/PO4 with ALP might be a lowcost, simple, available predictive marker of PHPT in Chinese individuals, particularly Chinese remote region where the method used to measure PTH cannot be done. Moreover, due to serum calcium level in NPHPT, Cl/PO4 combined with ALP level measurement have great potential to predict significant occurrence of NPHPT. Primary hyperparathyroidism (PHPT) is characterised biochemically by an inappropriately elevated parathyroid hormone (PTH) level and it is one of the most common endocrine disorders affecting human health1. Using the serum calcium level, PHPT can be subdivided into normocalcaemic primary hyperparathyroidism (NPHPT) and hypercalcaemic primary hyperparathyroidism. Wills first used the term NPHPT in the 1960s1. NPHPT is characterised by normal serum calcium levels and consistently high PTH levels2. NPHPT is not a common type of PHPT. Persistently elevated PTH and hypercalcaemia are the diagnostic markers of PHPT3. Several studies have used the oral calcium load to diagnose PHPT inpatients with NPHPT and asymptomatic patients4, 5. However, in clinical, we found PTH testing did not appear in the conventional inspection indicators, and the PTH testing equipment are expensive and time-consuming. And some Chinese remote areas had no equipment measuring PTH, Simultaneously, although serum calcium was measured in most hospitals, but serum calcium level was normal in the NPHPT patients. To improve the diagnosis of PHPT, we need to find additional, simple markers for diagnosing PHPT.
Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, 200233, China. Qianqian Wang and Xu Li contributed equally to this work. Correspondence and requests for materials should be addressed to J.H. (email: [email protected]) or L.W. (email: [email protected]) Scientific Reports | 7: 4868 | DOI:10.1038/s41598-017-05183-6
1
www.nature.com/scientificreports/ Reeves introduced the concept of the chloride/phosphate ratio (Cl/PO4)6. Some studies found that Cl/PO4 was a good tool for distinguishing PHPT from other causes of hypercalcaemia7–10. Furthermore, Mismar et al.11 reported that Cl/PO4 was predictive in normocalcaemic patients in an Indian population. Katelina12 and McComb9 et al. suggested that alkaline phosphatase (ALP) is a membrane-bound enzyme associated with the mineralization of bone tissue. The serum ALP level is elevated in 96% of patients with primary hyperparathyroidism13. But there have been no study evaluating predicting diagnostic value of Cl/PO4 combined with ALP in PHPT. Therefore, this study investigated the value of the two indicators combinatiom measurement as an auxiliary diagnostic method for PHPT diagnosis in a Chinese population, especially for predicting significant occurrence of NPHPT.
Materials and Methods
Study Population. From January 2003 to March 2015, 172 patients with PHPT in the General Surgery
Department of Shanghai Jiao Tong University Affiliated Sixth People’s Hospital were enrolled in our study. According to Chinese guidelines, for PHPT definition we used as main criteria a PTH level >65 and the presence of parathyroid adenoma based on intraoperative frozen and postoperative pathology, but not calcium blood level. PHPT can be subdivided into NPHPT and hypercalcaemic primary hyperparathyroidism using the serum calcium level. The exclusion criteria were as follows: all PHPT patients treated without surgery; secondary hyperparathyroidism; vitamin D deficiency; renal disease; hypercalciuria caused by other diseases; the use of diuretics; liver disease and other causes of an elevated PTH. The subjects were divided into two groups according to the serum calcium levels: 151 had a high serum calcium and PTH, while 19 patients were defined as NPHPT. During the same period, 50 clinical check-up healthy subjects from medical examination center of Shanghai Jiao Tong University Affiliated Sixth People’s Hospital were enrolled in our study. The inclusive criteria for them is as follows: All these participants had normal PTH levels, not suffering from PHPT disease, no family history of PHPT, normal renal function, and none were receiving medications known to influence these parameters such as sodium, potassium, ALP, phosphorus, chloride, calcium and PTH. The exclusion criteria of the control group is as follows: Patients were excluded if they had any disease that could affect electrolyte disorder (e.g. cancer, liver disease, cacotrophy, renal insufficiency, hypovolaemia and dehydration). Participants with using any related drugs such as diuretics were also excluded from the study. The study was approved by the Human Research Ethics Committee of Shanghai Sixth People’s Hospital, all experiments were performed in accordance with relevant guidelines and regulations. Each participant gave written informed consent.
Anthropometric evaluation and biochemical measurements. General information on the 222 par-
ticipants, such as gender and age, was obtained through inquiry. Anthropometric parameters such as height, body weight, and blood pressure were measured and the Body Mass Index (BMI) was calculated as weight/height2. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured enzymatically on a Hitachi 7600 analyser (Hitachi, Tokyo, Japan). Serum sodium, potassium, alkaline phosphatase (ALP), phosphorus, chloride, and calcium were measured using automated techniques before surgery. ALP was detected by AMP buffer method of the ALP kit (KH-G-C-012) obtaining from Shanghai Kehua Bio-engineering Co., Ltd (Shanghai, China). The normal range for ALP is from 14 to 112 U/L. We calculated the chloride/phosphate ratio (Cl/PO4) as chloride (mEq/L)/phosphate (mg/100 mL). The total serum calcium levels used in our research was adjusted for albumin. The formula to use is: corrected calcium = measured total serum calcium in mg/dL + 0.8*(4.0- patient’s serum albumin concentration in g/dL). Serum PTH was measured by using an electrochemiluminescence immunoassay (ECLIA) on an Elecsys autoanalyser (E170; Roche Diagnostic, Mannheim, Germany). All biochemical values were measured from the same blood sample collected after an overnight fast. Related indicators were detected by Department of Medical Laboratory in Shanghai Jiao Tong University Affiliated Sixth People’s Hospital. And the detection methods of related indicators had not changed.
Statistical analyses. Statistical analysis was performed using SPSS for Windows software (ver. 17.0; SPSS Inc., Chicago, IL, USA). Normally distributed data are presented as means ± standard deviation (SD). Non-normally distributed data determined using the Kolmogorov–Smirnov test are expressed as medians and interquartile range (25–75%). Two groups were compared using Student’s unpaired t-test. The composition ratio of categorical variables was calculated using the chi-square test. Pearson’s correlation was used to evaluate the association among the Cl/PO4 ratio, ALP and other general biochemical parameters. To analyse whether Cl/ PO4 and ALP might be related to PHPT independently, we applied logistic regression models to adjust for other clinical and biochemical variables. The predictive performance of each model was assessed using area the under the receiver operating characteristic (ROC-AUC) curve with 95% confidence intervals (CI). All P-values were two-tailed and statistical significance was considered as P
